Oil and Gas 101::: Directional Drilling ::: Amerex Corporation :::
Glossary of Terms :: Porosity, Permeability, Pressure :: Directional Drilling :: Oil Well Diagram :: Secondary Recovery :: Oil and Gas History
Until about twenty years ago, drilling an oil well was nothing more than a long straight hole in the ground. The only way to reach an oil deposit was to drill from directly above the intended formation. If the area was not accessible, either from an obstruction by man made objects or geophysical obstacles such as mountains, there would be no way to reach these deposits. The drilling industry began looking for the solution.
Several ideas were proposed as to how to go about getting to these inaccessible deposits. They all had the same basic principle in mind, which was to start the drilling from a location near the formation they were trying to access. From here, there were two theories that prevailed. The first being to position the drilling rig to the appropriate angle in order to strike the deposit from the starting point. This proved to be the most direct route to the formations, but because every starting angle was different, rig setup became increasingly more difficult. The second idea was to place a bend in the well bore at a desired depth and reach the formations horizontally. Since every well would essentially be the same, short of depths and lengths, drilling rig setup was less time consuming for each new well. The minimization of variables made the horizontal method a more reliable choice.
Once it was decided what method to use, exploration experts needed to decide on how to pull it off. Forming the arc was actually the easy part. The apparently rigid drill pipe sections are sufficiently flexible enough that each piece can be bent minimally without risk of structural failure. If you put enough of these bent sections together, you obtain an arc that is mathematically predictable. In fact, the most difficult part in the whole of horizontal drilling is steering. A breakthrough came with the implementation of down-hole motors that can rotate the drill bit at the bottom of the well without having to rotate the entire length of pipe. This gave drillers the ability to steer the bit. Over time, the ability to control the direction of the hole has allowed exploration to be more precise, rather than hit or miss.
The ability to drill horizontally has greatly reduced the number of wells needed to reach these same deposits. Some formations span thousands of feet laterally, but only sit in a five to thirty-foot layer of earth. A horizontal section of pipe drilled from the proper location could span the entire natural deposit. Although the costs are higher for horizontal wells, the amount of oil and gas produced, as well as the need for fewer offsets has made these wells in actual fact, more cost efficient, provided the formation warrents a horizontal drill.
The effect of horizontal drilling has been enormous throughout the industry. Oil fields once thought unreachable or dried up have found new life. Greater reserves are being accessed which were physically or economically inaccessible in the past. Maximum resources are being harvested with minimum danger to the surrounding nature. The impact of horizontal drilling will be felt in the energy industry for years to come.